SEARCH FOR THE ELUSIVE VACCINE
When scientists first started developing vaccines against HIV, they believed that it would take 10 years to find one. Now, more than two decades later, they seem no closer to success.
In an interview with Professor Lynn Morris, one of the scientists deeply involved in the search for an HIV vaccine in South Africa, Khopotso Bodibe explored where we stand when it comes to finding that ever-elusive vaccine.
Looking the opposite of a scientist – in jeans and a V-neck T-shirt – Morris has dedicated the last 14 years of her life to HIV research, the last half of which have been spent on vaccine investigations. Around a table in her office at the National Institute of Communicable Diseases, she speaks candidly about the frustrations of trying to find a vaccine.
“I am frustrated by the fact that, yes, we’re not making progress. But, I think what must be really frustrating is dealing with the participants and having to explain to people that this vaccine hasn’t worked must be very frustrating and very difficult,” says Morris.
Recently, scientists and researchers were sent back to the drawing board after the disappointing results of the STEP vaccine trial, conducted in the United States. Its sister trial in South Africa, was known as the HVTN 503 study or Phambili. So how much of a disappointment was the suspension of the trials?
“The latest vaccine trial was a real setback. It was a vaccine that had shown promise in animal studies, but also in earlier clinical trials in humans because it’s very good at stimulating what we thought were the right immune responses. People who had been vaccinated made what are called cytotoxic T-cells. Now, these are cells that are able to kill cells that are infected with (the) virus,” she explains.
“We thought if people had these killer T-cells in their body, if they did encounter the virus, they would be pre-armed and ready. So, that was really the basis of that vaccine – that it stimulated these good immune responses. However, when this vaccine was tested in what is called an efficacy trial… the vaccine did not offer them any protection.”
“…it’s useful to note that polio, for example, took 47 years from when it was discovered to having an effective vaccine.”
In fact, the study was ended after interim analysis of the US trial showed higher rates of infection in those given the vaccine. There were 33 HIV infections in the placebo group and a significantly higher 49 in the vaccine group.
For ethical reasons, the South African study also had to be stopped. To date, only one vaccine study has completed efficacy level research. But the results also proved disappointing. This begs the question: Why is it so difficult to develop an effective HIV vaccine when diseases such as small pox and measles, among others, have one?
Morris says that HIV presents possibly the most challenges of any virus. She explains that unlike with other viruses, “We’ve often been guided by the immune responses of people who’ve had these infections and who’ve gone on to clear the infection, as happens with many viral infections. Now with HIV, nobody has ever been infected with HIV and recovered… So, it means that the immune system itself is not able to do that. So, a vaccine has to actually do better than the human body does… And that’s one of the biggest challenges… We don’t know what immune responses we need to stimulate to make a protective HIV vaccine.”
The development of HIV vaccines has taken many forms over the years. The earliest vaccines made use of the outer surface proteins of HIV, called lollipops. Due to failure to elicit the desired immune response, this strategy changed over time. But even new technologies in HIV vaccinology are failing to succeed. Morris and many others in her field are now realising that it will be a long time before they can find an effective vaccine against HIV.
In the absence of a cure for AIDS, coupled with risky behaviour and other factors, including social ills, biological interventions such as an HIV vaccine has been seen as an absolute necessity to prevent millions from potential infection. As for how long it will take to find a vaccine, it’s useful to note that polio, for example, took 47 years from when it was discovered to having an effective vaccine.
Morris does believe that a vaccine is possible against HIV, but is hesitant to put a timeline on its development: “The message out there is that a vaccine isn’t around the corner,” and she adds, “even if we did have a vaccine, it wouldn’t be the complete answer because no vaccine is a 100% effective.”
Based on a radio interview by Khopotso Bodibe
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